* factorial using using iteration

* add ceil() to maths
* add combinations() to maths
* add floor() to maths

Maths/Floor.java

@@ -0,0 +1,32 @@
+package Maths;
+
+public class Floor {
+    public static void main(String[] args) {
+        assert floor(10) == Math.floor(10);
+        assert floor(-10) == Math.floor(-10);
+        assert floor(10.0) == Math.floor(10.0);
+        assert floor(-10.0) == Math.floor(-10.0);
+        assert floor(10.1) == Math.floor(10.1);
+        assert floor(-10.1) == Math.floor(-10.1);
+        assert floor(0) == Math.floor(0);
+        assert floor(-0) == Math.floor(-0);
+        assert floor(0.0) == Math.floor(0.0);
+        assert floor(-0.0) == Math.floor(-0.0);
+    }
+
+    /**
+     * Returns the largest (closest to positive infinity)
+     *
+     * @param number the number
+     * @return the largest (closest to positive infinity)  of given {@code number}
+     */
+    public static double floor(double number) {
+        if (number - (int) number == 0) {
+            return number;
+        } else if (number - (int) number > 0) {
+            return (int) number;
+        } else {
+            return (int) number - 1;
+        }
+    }
+}